Casting a degree of doubt on Yao Ming’s immediate and long-term NBA future, Rockets team physician Tom Clanton on Monday described the extent of the center’s foot injury. And with the league’s free-agent shopping season set to begin at 11 p.m. today, the Rockets will quickly discover how far the shock waves reach.

The fracture in Yao’s left foot has worsened and could be severe enough to threaten his entire next season or even his career, depending on the success of potential treatments he could choose, Clanton said.

Less than two weeks ago, Rockets general manager Daryl Morey said the team is committed to building around Yao.

“Yao,” Morey said before the latest test results, “is the cornerstone of our franchise now and in the future.”

Now Morey might have to start rebuilding without him.

Yao, who was hurt during this year’s NBA Western Conference semifinals against the Los Angeles Lakers, is scheduled to visit specialists around the country to choose a course of treatment. He could try a more conservative approach by immobilizing the foot in hopes the hairline fracture in his left tarsal navicular bone will heal on its own, as doctors predicted it would when Yao’s season ended May 8. Because Yao has no pain or other symptoms, Clanton said there is reason to be optimistic that approach could work.

But Clanton also revealed Monday that a CT scan showed Yao’s injury not only failed to heal as expected but has gotten worse, potentially requiring a surgical remedy.

“At this point, the injury has the potential for him missing this next season and could be career-threatening,” Clanton said. “One of the things we are trying to get is a consensus opinion on that, to make certain there is no option we are overlooking that would provide an earlier return or would be an option for treatment that he would prefer rather than doing additional surgery.”

Yao, Rockets owner Leslie Alexander and Yao’s agent, John Huizinga, were unavailable for comment. Morey said he would not discuss Yao’s injury or its ramifications until Yao chooses a treatment option and doctors offer a prognosis.

“We are not going to comment,” Morey said, “until we have all the facts.”

Free agent talks

Artest considered the Rockets a championship contender when he indicated last month that he hoped to remain with the team. The Rockets could find out quickly if he and other free agents still feel that way. Artest’s agent, David Bauman, declined to comment on the impact Yao’s injury might have on Artest’s decision.

The Rockets could be in a position to seek a replacement for Yao. If he is ruled out for all of next season, the team could request a disabled player exception to the salary cap, allowing it to sign a player for the value of the mid-level exception, which is 108 percent of the average NBA player’s salary (which last season was $5.6 million).

But that would be an extreme commitment for the Rockets, since it would force them to pay large penalties under the NBA’s luxury tax and to offer an expensive deal to a player who would theoretically be a backup when Yao returns.

That scenario also presents few attractive options. Forward Carlos Boozer and center Mehmet Okur of the Utah Jazz are considering opting out of their contracts. The Rockets could try to sign Orlando backup center Marcin Gortat, a restricted free agent, to an offer sheet for all or part of the mid-level exception and then hope the Magic don’t match the offer to retain him.

Tough decision ahead

After that, the top options might be power forwards able to play in the middle such as Brandon Bass, Antonio McDyess, Chris Andersen and perhaps former All-Star Rasheed Wallace.

The Rockets could face a tough decision even if Yao does return in the 2009-10 campaign. He has two years left on his contract and could opt out after next season. He had been considered a certain maximum-contract player, but the difficulty getting over his latest injury could impact the team’s thinking.

The Rockets are helped by the fact their other marquee player, guard Tracy McGrady, is attempting a comeback from microfracture knee surgery. McGrady is scheduled to begin on-court workouts in the coming weeks. Until then, the Rockets can’t estimate when he might return to competition.

For now, the emphasis is on getting Yao back on the court. The surgical treatment options could include placing a pin inside the foot; a bone graft; or even realigning the foot to operate differently. Cleveland Cavaliers centerZydrunas Ilgauskas underwent similar procedures, reducing his high arch to a flatter foot position. That option could be considered for Yao, Clanton said, though his arch is not as high as Ilgauskas’ was.

“That’s what we’re hoping to avoid, but that is certainly a realistic situation given his injury and the way the bone looked on the CT scan,” Clanton said. “The fact he is having no symptoms gives us reason for optimism.”

‘Shocking for him and us’

Yao had a pin inserted in the foot in February 2008 and in less than six months was ready to play in the Olympics and in 77 regular-season games last season. But Clanton said there is concern that a more extreme procedure might be warranted, even though Yao’s current injury is considered less severe.

“At this stage, he is having no symptoms or physical signs,” Clanton said. “He has no tenderness, no swelling, no redness. When he came back in, he was feeling like everything was perfect, and he would start rehabilitation and get ready to play. The findings on the CT were shocking for him and for us.

“You don’t treat a CT scan; you treat a patient. We are looking for every reason to treat this on clinical findings but don’t want to put him at risk for a greater fracture.”